SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b14d7ae47b918ee3838422785c02fb448ee7055f10859deb231a1eed882a3071' 
  AND token = '/nTLO2mB53YNIHMsHMTEIZLOc80RCc8ceNmazhtOBqI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}